Right, but that’s likely not the case. You’d have to figure not only hours spent to figure salary, but you’d also have to apportion mower time, maintenance, depreciation, etc to just the football field compared to the other things being mowed. Then there are things like fertilizer - how much did you spend overall and how much went on the football field? Watering costs? Gallons per minute used only on the football field, well or city water, electric used to run the pumps…
I agree that if a school was doing an analysis of whether to turf or grass, you’d need to do studies like these. But in general, back of the envelope math can tell you most of these small schools (especially those without soccer) aren’t going to benefit financially from turf.